The present invention relates to a method for producing a dental product or other product for the human body using material in powder form. In a first manufacturing stage, with the aid of a mould tool, the product is given a shape which is larger than its final shape, and in further manufacturing stages the product is subjected to working and material shrinkage/sintering to obtain the final shape. The invention also relates to a product intended as a component in a dental application or other application in the human body, where it cooperates with members in the form of implants, attachment parts for implants, bones, for example dentine, tooth remnants, etc. The product is made up from worked and sintered and worked powder material. The invention also relates to a use of the product of the said type.
It is already known to make products or bodies of the type in question using powder material in the form of ceramic powder. In this context, it is known to use mould tools in which the ceramic powder is applied. The mould tool is given a larger shape or size. The ceramic powder is applied in the mould and is exposed to compression forces, after which the compressed body is worked and shrunk further in a sintering process.
Reference may be made in entirely general terms to manufacturing principles which are proposed and used in the Procera technique for manufacturing products of the type in question and where, inter alia, final outer shapes are produced from enlarged outer shapes.
Thus, from U.S. Pat. No. 5,192,173 (with the same inventor) it is already known to create a linearly enlarged shape on the tool in question. Reference is also made to European Patent 384,908 B1 same inventor) which shows that a linearly enlarged body can be subjected to a sintering process so as to be given its desired final shape.
It is also known to make products or bodies of the abovementioned type from metal. The outer shape of the product is in this case turned or milled from a blank. An electro-oxidation tool with an outer shape corresponding to the inner shape of the product is made and is used for producing the inner surface of the product by means of electro-oxidation.
The production of ceramic products and metal products has hitherto had to be carried out using two completely different techniques which have been employed within the technical area of dental technology and technology related to the human body. This has divided resources for manufacturers of these types of products and other products for the human body. There is a requirement for the technical resources to be brought together more effectively and, for example, for the same types of personnel to be used to produce caps, spacers, bridges, etc. The invention aims to solve this problem among others.
In the sector concerned with the manufacture of products, for example caps, made of metal material, consideration has been given to imitating the principles used for ceramic caps or equivalent. However, there has been strong technical opposition and considerable bias against its being possible, in serial manufacture of structurally robust caps/products which are to function in a technically severe environment (in the patient""s mouth) and therefore must have strict strength requirements and at the same time upholding the precision requirements, to be able to manufacture caps/products in the same way as in ceramic production.
The invention counters this strong technical opposition and bias and takes a completely new approach in order to permit a new type of manufacture of caps/products of the type in question.
There is a need to technically simplify, and to make less expensive, the previous manufacture of caps and other dental products using mechanical working and electro-oxidation. The invention solves this problem too and now proposes principles in which previous strength and precision requirements (0.2 xcexcm) can also be maintained.
In connection with the new principles for production of caps/products made of metal, there is a need to be able to vary the strength requirements, precision requirements, manufacturing process, etc. The invention solves this set of problems too and is not confined to individual procedures for achieving the requirements set. The new principles are especially suited to titanium powder which has the best biocompatible character. However, there have been strong doubts as to whether it is in principle possible to make caps and similar products from titanium powder material.
The feature which can principally be regarded as characterizing a method according to the invention is that metal powder is applied to the mould tool, and that the mould tool with the applied metal powder is placed in pressure-generating equipment where the powder applied to the mould tool is subjected to compaction pressure which compacts the powder so that at least an 80 percent basic density is obtained in the material, and that thereafter the material compacted on the mould is first machined and then removed from the mould tool, after which the said material shrinkage/sintering stages are carried out so that the final shape is obtained, and at the same time a porosity of at most about 6 percent by volume, preferably at most 2 to 3 percent by volume, is obtained in the sintered product.
In one embodiment, the outer shape of the product is produced or worked (in an enlarged state), after which the product""s final shape is obtained in the sintering process. The product is given a distinct or substantial homogeneity with respect to the distribution of the porosity. The material of the product is treated in such a way by the new method that it becomes ductile (substantially ductile) so that there is no tendency to crack or fracture under the effect of force.
In one proposed embodiment, the powder, on application to the mould tool in question, or stamp, is arranged in a powder-receiving unit in which the outer shape of the stamp can be lowered so that the powder surrounds the outer surface of the stamp. The powder can in this case be poured or applied into a tube-like or rubber bladder-like powder-receiving unit with elastic wall, which for example can be a silicone wall, via which the pressure is allowed to act in the pressure-generating equipment. The powder material chosen is preferably titanium powder which can comprise powder of the type TWC-f, whose particles are deformed by the compaction or the action of pressure in the pressure-generating equipment. The de-moulding of the compacted metal powder from the mould tool or stamp is preferably done in a bath of liquid nitrogen/air, and the stamp and the metal powder are in this case chosen with different coefficients of expansion, which means that the de-moulding is made considerably simpler. The sintering process in carried out in a vacuum sintering appliance.
In one embodiment, a number of mould tools or stamps which represent a number of possible unique or individual inner shapes of the product are produced. The respective stamp is selected from a selection of stamps depending on the inner shape which the product is to be given.
The metal powder material compacted on the mould tool or stamp is machined by turning or milling, the mould tool/stamp being arranged together with the compacted material. The product can in this case be given a shape with a cap-like character where the inner shape of the product corresponds to the outer surface of the mould tool/stamp, and the outer shape of the product is machined, for example by turning or milling. The turning or milling is preferably carried out from the upper part of the cap-like product and working downwards.
The mould tool/stamp is designed with a degree of enlargement which is preferably chosen within the range of enlargement immediately over 0% and up to about 12%, or immediately below 12%. The compaction pressure is chosen within the range of 300 to 900 MPa. The degree of enlargement used within the said range can be determined as a function of the compaction pressure used. The shrinkage or sintering operation provides a shrinkage or sintering which is slightly below the chosen degree of enlargement. The product is produced with inner or outer shapes produced with a degree of precision of about 20 xcexcm. The product is preferably a thin-walled product, with values within the range of 400 to 600 xcexcm. The product or the cap can also be produced with a precision which provides play of 100 to 400 xcexcm in relation to the opposing surface of the dental member in question or the dental component in question.
Titanium powder is preferably used, but it is possible per se alternatively to use gold alloy or steel powder material.
The new product can principally be regarded as being characterized by the fact that the powder material consists of or comprises metal powder material deformed by compaction and sintered and having a porosity of at most 6, preferably 2 to 3, percent by volume.
The product is preferably (substantially) ductile and is (substantially) homogeneous and with evenly distributed porosity.
In a preferred embodiment, the product has essentially the shape of a cap. The product is thin-walled and can have a wall thickness or wall thicknesses within the range of 400 to 600 xcexcm. The product has a precision fit on its inner and/or outer shapes of about 20 xcexcm. The product or the cap forms a self-supporting structure or construction whose strength properties correspond to those of a conventional product for the dental application or other application in the human body. The product or the cap preferably has a degree of compaction which allows it to be worked by cutting tools, for example turning or milling, when producing the outer shape. The product consists or is made of titanium powder material in the first instance, although gold alloy or steel powder can alternatively be used.
A use of the product of the said type is characterized by the fact that metal powder which is compacted and sintered to a porosity of at most 6, preferably 2 to 3, percent by volume is used as powder material. Titanium powder is preferably used for producing a self-supporting product, for example cap.
A surprising effect is that the strict precision requirements in accordance with the present case can be obtained with such a considerable degree of sintering of the metal powder, especially titanium powder, in question here.
The features which have been proposed above permit a considerably simplified manufacture of metal caps and products for dental application. Conventional press moulding and de-moulding principles as well as sintering principles can be used, so that technically simple and wellxe2x80x94proven operations are possible. Tests carried out with respect to strength and precision show surprising effects in that the cap/product can be made at least as strong and accurately as caps/products produced using conventional techniques and by conventional methods. In addition, it is possible to control the manufacturing process so that discoloring of the product""s surface(s) is eliminated. Particular advantages of the invention are obtained when titanium powder is used. Titanium powder can give strong, load-bearing products or caps.